抄録
Measurements of 210Pb (half life of 22.3 y) at various depths down to 180m in an ice core from an Arctic glacier, Åsgårdfonna, in northern Spitsbergen have been made. The activity of 210Pb was obtained by counting α-rays from its daughter nuclide, 210Po (half life of 138d). The specific activity of 210Pb at the surface of the glacier, 110mBq/kg, decreased exponentially with depth to 4.72mBq/kg at about 30m depth. Below 30m, the activities were nearly constant and the average value from 30m to 180m was 4.85±1.33mBq/kg. This result indicates that the atmospheric 210Pb deposit onto the glacier decays as a function of time at a rate controlled by its half life. The α spectrometric method for the determination of 210Pb in an ice sample and the result of the ice core dating are described in this paper.
